PROJECT SUMMARY The overall goal of this project is to determine whether TBI-induced inflammatory changes result in peripheral organ damage that is dependent on activation of the inflammasome by extracellular vesicles (EV) and ASC specks. Our recent work has shown that a crucial part of the TBI-induced systemic inflammatory response involves release of extracellular vesicles containing a cargo of innate immune proteins that are secreted from damaged central nervous system (CNS) tissue. Importantly, EV and ASC specks from TBI animals induce inflammasome activation in peripheral organs. The specific aims of this proposal will determine the cellular and molecular mechanisms regulating EV- and ASC speck-mediated innate immune inflammatory reactions in peripheral organs after TBI. The hypothesis of this study is that EV and ASC specks play a central role in innate immune signaling by carrying inflammasome proteins to peripheral organs after TBI, thus causing tissue injury. Moreover, neutralization of secreted ASC with a monoclonal antibody decreases peripheral organ damage after TBI, resulting in improved histopathological outcomes. Aim 1 will determine if TBI alters the composition of EV proteins in brain, peripheral organs and bodily fluids. These studies will delineate a protein profile of EV proteins after TBI. Aim 2 will establish if ASC specks accumulate in brain and peripheral organs after TBI and induce an inflammatory responses leading to pyroptosis. We will investigate whether the activation of inflammasomes in vivo leads to the appearance of ASC specks and whether the deposition of ASC specks in tissues induces the recruitment of neutrophils and lymphocytes, thus contributing to the inflammatory milieu in peripheral organs. Aim 3 will determine the therapeutic effects of antibody neutralization of the inflammasome on histopathological outcomes after TBI. These studies will provide critical information about the activation patterns of innate immunity regulated by EV and ASC specks in the CNS, and identify relevant therapeutic targets to control inflammation following TBI and other neurodegenerative disorders.